D - F

D

Daily range of temperature The difference between the maximum and minimum temperatures for any given day. 
Demography Scientific study of population is known as Demograhy.
it was started by Thomas R. Malthus (1798).
Demographic Transition It is the Zero population growth when birth rate and death rate become equal.

Density The ratio of the mass of a substance to the volume occupied by it.

Deposition A process that occurs in subfreezing air when water vapor changes directly to ice without becoming a liquid first. (Also called sublimation in meteorology.)

Deposition nuclei Tiny particles in the atmosphere that serve as the core of tiny ice crystals as water vapor changes to the solid form. These are also called ice nuclei.

Desert One of two types of dry climate-the driest of the dry climates.

Dew Water that has condensed onto objects near the ground when their temperatures have fallen below the dew point of the surface air.

Dew point (dew-point temperature) The temperature to which air must be cooled (at constant pressure and constant water vapor content) for saturation to occur. When the dew point falls below freezing it is called the frost point.

Drizzle Small drops between 0.2 and 0.5 mm in diameter that fall slowly and reduce visibility more than light rain.

Drought A period of abnormally dry weather sufficiently long enough to cause serious effects on agriculture and other activities in the affected area.

Dry adiabatic rate The rate of change of temperature in a rising or descending unsaturated air parcel. The rate of adiabatic cooling or warming is 10ºC per 1000 m (5.5ºF per 1000 ft).

Dry climate A climate in which yearly precipitation is not as great as the potential loss of water by evaporation.

E

Ecological Efficiency "The percentage ratio between energy flow at different trophic level of a food chain".
It is also called as progressive or reproductive efficiency.
Ecological Pyramid Graphical representation of different ecological parameters such as number of individuals, biomass and energy in a food chain or in different trophic levels.
Example-
1.Pyramid of Energy
2. Pyramid of Number
3. Pyramid of Biomass
Ecology The term Ecology was coined by Reiter (1868 A.D.).
It is the scientific study of inter-relationship of organisms with one another and with the environment.
It was called "study of reciprocal relationship" by Earnst Haeckel (1869 A.D.).
Ecosystem The term ecosystem was proposed by A.G. Tansley (1935).
"Any unit that includes all the organisms i.e. the communities in a given area, interact with the physical environment, so that a flow of energy leads to clearly defined trophic structure, biotic diversity and material cycling within the system, known as ecosystem.
Example- Forest ecosystem, Pond Ecosystem etc.
Ecotone A transitional zone where two or more communities meet and intergrade is known as ecotone.
or
The zones transition between adjacent ecological system, having a set of characteristics uniquely defined by space and time scale and by strength of the interactions between them (J. Davle, 1997).
Edge A transitional zone where two or more communities meet is called an edge.
Edge Effect It is effect of juxtaposition* of contrasting environments of an ecosystem. This term is commonly used in conjunction with the boundaries between natural habitats, espacially forests disturbed or developed land.
*Juxtaposition- an instant or act of placing two things close together or side by side.

Eddy A small volume of air (or any fluid) that behaves differently from the larger flow in which it exists. 
Energy Budget "the balance between income and expenditure of energy in an ecosystem".
First energy budget was put forward by Lindeman in 1942 for an entire biological community that of 'Cedar Bog Lake' in Minnesota.

Environmental lapse rate The rate of decrease of temperature with elevation. It is most often measured with a radiosonde.

Equilibrium vapor pressure The necessary vapor pressure around liquid water that allows the water to remain in equilibrium with its environment. Also called saturation vapor pressure.

Equinox The time when the sun crosses the plane of the earth's equator occurring about March 21 and September 22.

Exosphere The outermost portion of the atmosphere.

 

F

Fog A cloud with its base at the earth's surface. It reduces visibility to below 1 km.

Food Chain A series of groups of organisms called trophic levels in which there is repeated eating and eaten by so as to tranmit food energy, is called as food chain.
Food Web It is a network of food chains which is become interconnected at various trophic levels so as to form a number of feeding connections amongst different organisms of a biotic community.